Optical recording medium with wobbled grooves and interconnecting pits

ABSTRACT

An optical recording medium for accurately deriving the address information or the disc rotation control information despite narrow track pitch and for recording signals to a high density, and a method and apparatus for recording and/or reproducing such optical recording medium. The optical recording medium has a wobbled groove and pits formed at a pre-set interval in an area between turns of the wobbled groove. The recording/reproducing method includes controlling rotation of the optical recording medium by a wobbled signal from the groove and detecting the position on the optical recording medium of a recording signal by pit signals detected from the pits. The recording/reproducing apparatus includes a detection device for detecting the wobbled signal from the groove and a detection device for detecting pit signals from the pits. The rotation of the optical recording medium is controlled by the wobbled signals detected from the groove and the position on the optical recording medium of the recording signal is detected by the pit signal detected from the pits.

This is a continuation of application Ser. No. 08/825,890, filed Apr. 2,1997, now U.S. Pat. No. 6,075,761.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an optical recording medium having a wobbledgroove, more particularly, to a novel optical recording medium capableof recording signals to a high density. The invention also relates to amethod and apparatus for recording and/or reproducing such opticalrecording medium.

2. Description of the Related Art

The CD-R disc, used in, for example, a so-called compact disc recordablesystem (CD-R), has a wobbled groove. The sector information, inclusiveof the address information, is recorded by modulating the wobbledsignal.

Specifically, in a CD-R recording and/or reproducing apparatus, thewobbled signal having 22 kHz as carrier wave, is detected by a recordingand/or reproducing light spot converged on the groove. A data stringincluding the address information is detected by FM demodulating thewobbled signal.

In a system in which the address is arrayed at the leading end of thesector, the address information and the recording information arerecorded time-divisionally, so that the recorded signals becomediscontinuous signals. With the present system, the data can be recordedcontinuously. Such feature is meritorious for an application in whichemphasis is placed on interchangeability with the read-only disc onwhich the signals are recorded continuously.

In a method of recording the address information by modulating thewobbled signal, if the track pitch, which is the distance betweenneighboring groves, is reduced, the leakage of the wobbled signal fromthe neighboring groove is increased, thus lowering the S/N ratio of thewobbled signal. The address information not only cannot be demodulatedcorrectly, but also the carrier wave of the wobbled signal, required forrotational control of the disc, becomes difficult to detect thus givingrise to obstructions in rotational control of the disc.

Since it s necessary to reduce the track pitch for recording the signalto a high density, it becomes necessary to reproduce the addressinformation correctly despite the narrow track pitch.

Also, in the above system, the recording and/or reproducing spot on thedisc derived from the reproduced address information depends as to itsposition accuracy on the frequency of the carrier wave and issubstantially on the order of the wavelength of the carrier wave. On theother hand, the frequency of the carrier wave, that is the wobblingfrequency, needs to be selected to a lower value in order to avoidadverse effects on the recording signal. In the case of the CD-R, thewobbling frequency is 22 kHz, with the wavelength on the disc being 54μm.

If data is recorded discontinuously, that is with interruptions, anddata is recorded subsequently in the non-recorded portion, it isnecessary to record data in correct positions on the disc. If correctrecording is not possible, a so-called gap needs to be provided forabsorbing errors in recording positions from one recording data unit toanother for avoiding overlapping between recording data.

Since the gap reduces the recording capacity on the disc, the gap lengthneeds be reduced to as small a value as possible. However, theabove-mentioned accuracy is not sufficient.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an opticalrecording medium in which the address information and the disc rotationcontrol information can be correctly obtained despite the narrow trackpitch to enable the signal to be recorded to high density.

It is another object of the present invention to provide a method andapparatus for recording/reproducing the optical disc.

In one aspect, the present invention provides an optical recordingmedium having a wobbled groove and pits formed at a pre-set interval inan area between turns of the wobbled groove.

In another aspect, the present invention provides a method for recordingand/or reproducing signals to an optical recording medium having awobbled groove and pits formed at a pre-set interval in an area betweenturns of the wobbled groove. The recording method includes controllingrotation of the optical recording medium by a wobbled signal from thegroove and detecting the position on the optical recording medium of arecording signal by pit signals detected from the pits.

In another aspect, the present invention provides a recording and/orreproducing apparatus including an optical recording medium having awobbled groove and pits formed at a pre-set interval in an area betweenturns of the wobbled groove, detection means for detecting a wobbledsignal from said groove and detection means for detecting pit signalsfrom the pits, wherein rotation of the optical recording medium iscontrolled by the wobbled signals detected from the groove and whereinthe position on the optical recording medium of the recording signal isdetected by the pit signal detected from the pits.

With the above configuration of the present invention, the addressinformation and the rotation control information for the opticalrecording medium can be obtained accurately despite narrow track pitchthus contributing to high density recording.

The response speed and reliability of rotational control of the opticalrecording medium may also be improved simultaneously. For example, ifrotation of the CLV disc is controlled by only land pre-pits, thesepre-pits cannot temporarily cannot be detected if the linear velocity ischanged significantly due to random accessing, such that considerabletime is consumed until the pre-pits are again detected to resume therotational control. This inconvenience is resolved by using the wobbledpits and the pit signals simultaneously.

In addition, it is possible with the present invention to derive theaddress information more accurately and with high time precision than ispossible with the conventional technique.

Moreover, if, with the optical recording medium of the presentinvention, the wobbled signal and the address signals are read by thesole beam spot, it becomes possible to detect the playback signalcorresponding to the recording signal, servo signals (focusing servo andtracking servo signal), wobbled signal and the address information intheir entirety, thus simplifying the recording/reproducing apparatus andenabling the recording/reproducing apparatus to be manufactured atreduced cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an example in which a pit is formedat the center of wobbling.

FIG. 2 is a schematic view showing an example in which the wobblingamount is maximum and a pit has been formed at a position proximate to aneighboring groove.

FIG. 3 is a schematic plan view showing essential portions of an exampleof a groove and a pit in an optical recording medium embodying thepresent invention.

FIG. 4 is a waveform diagram showing a pulse signal obtained from a pit.

FIG. 5 shows a typical modulation of a synchronization pattern and adata pit.

FIG. 6 shows an example of a recording format for the addressinformation.

FIG. 7 is a circuit diagram showing an example of a signal reproducingcircuit.

FIG. 8 is a waveform diagram showing an example of a playback signal incase the frequency of the wobbled signal and that of a pit signal are ina integer ration relationship to each other.

FIG. 9 is a waveform diagram showing an example of a playback signal incase the wobbled signal and pit signal are in phase with each other.

FIG. 10 is a waveform diagram showing an example of a playback signal inwhich synchronization signals are recorded in both the wobbled signaland the pit signal.

FIG. 11 (including subparts A-F) is a timing chart in case the wobbledsignal and the pit signal are in phase with each other.

FIG. 12 is a block diagram showing an example of a playback circuit in areproducing apparatus.

FIG. 13 (including subparts (a)-(d)) is a timing chart in casesynchronization signals are recorded in both the wobbled signal and thepit signal.

FIG. 14 is a timing chart in which a pre-pit string leading end judgmentsignal is inserted as a wobbled signal.

FIG. 15 is a schematic plan view showing a modification of the grooveand the pit.

DESCRIPTION OF THE INVENTION

An optical recording medium according to the present invention has awobbled pre-groove and pits are formed at pre-set intervals in an areadefined between these grooves. The wobbled signal for the groove and thept signal for the pits are used in combination for enabling high-densityrecording.

The pits are formed in an area defined between neighboring grooves, thatis in a land. The pits may be in the form of usual pits or may be formedcontinuously between neighboring grooves as cut-outs in the landsinterconnecting the neighboring lands.

These pits include the sector information inclusive of the sync pits oraddress pits, and the address information is obtained by the sectorinformation. However, in the present invention, such sector informationis not always necessary such that it may be only necessary to provideonly sync pits or address pits. The sync pits indicate the startposition for the sector information and are formed as two pits arrangedin proximity to each other or as pits having pit lengths different fromthose of the other pits and hence can be detected as being distinct fromthe remaining pits.

On the other hand, a groove may have the wobbled signal of a solefrequency or may have the sector information in which the address datahas been recorded by modulation.

The sector information is the information associated with the sector ofthe recording data or a cluster which is a set of recording datasectors, and includes the synchronization signal and/or the addressdata.

The above groove or pit may be used in optional combination, such that,for example, the combination of the groove having the wobbled signal ofa sole frequency and sync pit or address pit, the combination of thegroove having the wobbled signal which is modulated for recording thesector information, such as synchronization signal or address data, andthe sync pit or address pit, or the combination of the groove having thewobbled signal which is modulated for recording the sector informationand pits of a pre-set interval, may be employed.

If, in these combinations, the combination of the groove having thewobbled signal of a sole frequency and sync pit or address pit isemployed, the synchronization information and the address informationcan be reliably produced by these sync pits and address pits, while thedisc rotation control information can be positively produced by thewobbled signal.

If the wobbled signal is the signal of a sole frequency, any leakagesignal from a neighboring groove is precisely of the same frequency asthe frequency of the signal for detection, so that the effect of leakagetakes the from of slow changes in amplitude in the wobbled signal fordetection, and hence the sole frequency for detection cannot be detectedeasily.

If the combination of the groove having the wobbled signal which ismodulated for recording the sector information, such as synchronizationsignal or address data, and the sync pit or address pit, is used, thesynchronization information or the address information is recorded induplicate in the groove and the pit, thus assuring increased accuracy isreliability.

If, when the groove and the pit are used in combination, the pitposition is formed at random relative to the groove, there is a fearthat the resulting playback signal is fluctuated in signal leveldepending on the pit position to render it difficult to detect the pitcorrectly. There is also a fear that the circuit for generating clocksin the reproducing apparatus becomes complex in structure.

For overcoming this drawback, it is desirable that the relation betweenthe wobbled frequency fw (mean frequency) and the pit frequency fp be aninteger number relation as defined by the following equation:

M fw=N fp

where M and N are integers.

Stated differently, the wobbling period Tw and the pit period Tp arerelated to each other by an integer number relationship to each other:

M Tw=N Tp

where M and N are integers.

Meanwhile, the wobble period Tw is an average wobbling period and thepit period Tp is an interval which, if the pits are formed at aninterval equal to a pre-set integer number multiple of the pre-setinterval, is equal to such preset integer number multiple interval. Onthe other hand, in case two consecutive pits are sync pits, these twopits are deemed as a sole pit and the period between these two pits isdisregarded in setting the pit period Tp.

If the wobbling frequency fw and the pit frequency fp are related eachother by an integer number relationship as described above, it becomespossible to unify reference clocks into one or use a sole voltagecontrolled oscillator, thus simplifying the clock generating circuit ofthe recording and/or reproducing apparatus.

In addition, it becomes possible to generate a signal synchronized withthe pit period from the wobbled signal by exploiting the PLL, therebyenabling the pits to be detected correctly.

Alternatively, the wobbling phase and the pit phase may be matched toeach other for enabling correct pit detection.

That is, by associating the pit position with a pre-set phase ofwobbling and by forming pits at a constant wobbling amount (meanderingamount of the groove), the pit detection signal may be stabilized forenabling the pits to be detected correctly.

In this case, a pit P may be formed at a wobbling center position of agroove G (a position corresponding to the smallest wobbling amount), asshown in FIG. 1. Alternatively, the pit P may be formed at a positionproximate to the neighboring groove and corresponding to the maximumwobbling amount, as shown in FIG. 2. In the former case, cross-talk fromother grooves becomes minimum, whereas, in the latter case, the pit canbe detected only by the signal level without removing wobbling signalcomponent.

If the sector information inclusive of the synchronization informationor the address information is recorded in the wobbled signal, and thepits include the sector information, such as the sync pits or addresspits, it is desirable that the synchronization information of thewobbling signals and the sector information, especially the sync pits,be at a pre-set positional relation to each other. For example, thesynchronization signal by wobbling is recorded within one pit periodahead of the sync pit in the reproducing direction.

By previously comprehending the position of the synchronization portionof the pit address from the wobbled signal, the pit addresssynchronization can be detected more correctly, as a result of which thepit address can be read out more reliably.

For recording/reproducing the above-described optical recording medium,disc rotation is controlled using a signal detected from a wobbledgroove, and the position of the recorded signal is controlled by theinformation detected from the pits formed in the land.

The recording/reproducing apparatus can be simplified in structure byreading out the wobbled signal and the pit signal simultaneously by thesame beam spot using the push-pull method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, preferred embodiments of the presentinvention will be explained in detail.

FIRST EMBODIMENT

An optical disc of the present embodiment is a write-once type disc, 12cm in diameter, having a recording film of an organic dye on whichrecording can be done using a laser beam having a wavelength of 635 nm.

The disc is formed of polycarbonate and is produced by injection moldingwith a guide groove and a land between neighboring turns of the guidegroove.

The groove is approximately 0.25 μm in width and approximately 70 nm indepth and is formed as a continuous spiral groove from the inner rim tothe outer rim, with the groove interval or track pitch of approximately0.74 μm.

The wobbled signal of a sole frequency is recorded as the informationfor controlling the rpm of the disc and the clock frequency of therecording signal. The wobbling means slight meandering of the groove inthe radial direction of the disc. In the present embodiment, themeandering width is 20 nm and the meandering period is approximately 30μm. Therefore, if the disc is rotated at a linear velocity of 3.5 m/secfor reproducing the wobbled signal, the frequency is approximately 120kHz.

In a land between neighboring turns of the groove, there is formed, as apit for recording the address information (address pit), a grooveapproximately 0.3 μm in width and approximately 70 nm in depth, as isthe guide groove.

Referring to FIG. 3, schematically showing the guide groove and theaddress pit, address pits 2 are formed at a pre-set interval in an areabetween neighboring turns of the wobbled guide groove 1. The addresspits 2 are formed continuously between neighboring turns of the grooveand are formed as grooves extending along the radius of the disc.

The address pits are formed at an interval of approximately 0.2 mm inassociation with 1/0 of the information. That is, there is an addresspit at a position corresponding to the information 1, while there is noaddress pit at a position corresponding to the information 0. Therefore,the presence or absence of the address pit corresponds to the 1/0 of theinformation.

FIG. 4 shows a signal obtained an scanning a beam spot B along thegroove. Specifically, there are obtained pulses of one polarity by theinner rim side address pits and those by the outer rim side address pitsof the opposite polarity. It suffices if the address information isdetected based on one of these two sorts of pulses.

In the present recording system, it may be presumed that, if æ0s of theinformation occur in succession, the state of absence of the addresspits occurs in succession to render it difficult to detect address pits.In the present embodiment, the recording information is previouslybi-phase modulated so that the number of contiguous æ0s will be two atthe maximum.

However, since the out-of-rule pattern of 000111 is provided in thesynchronization signal for facilitating detection of the synchronizationsignal, thee is a portion in the synchronization signal domain in whichaddress pits are not recorded for three contiguous channel bits.

FIG. 5 shows an example of modulation of data bits and thesynchronization pattern. The synchronization pattern is 0110001110001110thus containing three contiguous channel bits of 0 and 1 which are notprovided in the modulation rule.

The data bits are modulated so that 0 and 1 correspond to 1-0 and 0-1,respectively, so that æ1s or æ0s contiguous for 3 or more channel bitsare not contained in the data portion.

FIG. 6 shows an example of the recording format for the sectorinformation. The sector information is made up of a sum total of 208channel bits, of which the leading 16 channel bits represent thesynchronization pattern. The address data of 8 bytes is followed by 4bytes of parity for error correction by the Reed-Solomon code.

In the present recording format, since up to 2 bytes can be corrected bythe four bytes of parity, the address data can be correctly detected ifoptional two channel bits of the 208 channel bits of the sectorinformation are in error.

Next, signal reproduction of the above-described optical disc isexplained. Specifically, the method of simultaneously reading out thewobbled signal of the groove and the address signal of the pits by onebeam spot is explained.

Referring to FIG. 7, which is a block diagram of a signal reproducingcircuit, the return light from a beam spot B converged on the groove 1is photo-electrically converted by four-segment PIN diode detectors A,B, C and D and I-V converted to produce signals A, B, C and Dcorresponding to the respective diodes.

Of these signals, the sum of the signals (A+B+B+C) represents theplayback signal of the recorded signal. The sum signal is compensatedfor frequency response for recording/reproduction by an equalizercircuit 11 and converted to binary signals by a convert-to-binarycircuit 12 to produce playback signals, from which clocks for theplayback data are produced by a PLL circuit made up of a phasecomparator 13 and a voltage controlled oscillator (VCO) 14.

If the calculation of A−B+C−D is performed on the signals A, B, C and D,focusing error signals of the astigmatic system are obtained.

The focusing error signal is sent via phase compensation circuit 15 to afocusing driving circuit 16 from which a focusing driving signalcontrolling the focusing position of an objective lens is outputted.

If the calculation of A+B−C−D is performed on the signals A, B, C and D,tracking error signals of the push-pull system are obtained. Since thissignal is a signal corresponding to the relative position in the radialdirection of the groove and the beam spot B, the wobbled signal of thegroove is reproduced simultaneously. At a position in which an addresspit is formed, a positive pulse or a negative pulse is detecteddepending on whether an address bit is on the inner rim side or on theouter rim side with respect to the groove. These positive or negativepulses are similarly included in the signal (A+B−C−D).

First, this signal (A+B−C−D) is passed through a low-pass filter (LPF)17 to take out only the tracking error signal which is sent via a phasecompensation circuit 18 to a tracking driving circuit 19 for outputtingthe tracking driving signal.

For detecting pulse signals generated by the address pits, there isemployed a high-pass filter (HPF) 20 suppressing the signal less than130 kHz for avoiding the effect of the noise of the low frequency rangecaused by, for example, meandering by wobbling.

Since the wobbled signal is a narrow-band signal, a wobbled signal of anoptimum S/N ratio can be obtained by employing a band-pass filter (BPF)21 capable of passing the narrow band. The resulting wobbled signal isconverted to binary signals by a convert-to-binary circuit 22. Theresulting bi-level data is compared by a frequency comparator circuit 23to a reference frequency for producing a spindle motor control signal.

As described above, it is possible with the present embodiment toproduce all signals required for signal reproduction using a solefour-segment PIN diode detector.

SECOND EMBODIMENT In the present embodiment, various combinations of thewobbled pits are explained.

In a first example, wobbling of a sole frequence and pits having ainteger number relation with respect to the frequency of the wobbledsignal is explained.

The signal obtained in this case is as shown in FIG. 8, from which it isseen that pit signals Sp are detected at an interval equal to an integertimes the period Tw of the wobbled signal Sw, that is at an intervalequal to an integer times the pit period Tp.

In a second example, pits are formed in phase with the modulated wobbledsignal. In the present example, pits are formed at positions proximateto the neighboring groove, corresponding to the maximum wobbling. Thepit signals Sp are positioned at apices of the wobbled signal Sw andpits are detected based only of the signal level of the pit signal Sp,as shown in FIG. 9.

In FIG. 9, the pit signal Sp is generated by the pit formed on the innerrim side of the groove during tracking. On the other hand, the pitsignal Sp is generated by the pit formed on the outer rim side of thegroove.

In the first example, pit signals are detected after removing thewobbled signals from the pit signals by a high-pass filter. In thepresent example, the wobbled signal is passed through the high-passfilter and pits are detected by comparing the pit signal Sp inclusive ofthe wobbled signal with the detection level L. The reason is that, ifthe frequency band of the wobbled signal is close to that of the pitsignals, it may be premeditated that difficulties are met in frequencyseparation by the high-pass filter.

In the present example, the pits on the inner rim side of the groove arerecorded at positions corresponding to the maximum wobbling of thegroove towards the inner rim. In this case, the outer rim side pit sformed at a maximum wobbling position towards the inner rim of an outerrim side neighboring groove.

The wobbled signal of a given turn of the groove and that of aneighboring turn are not necessarily coincident with each other.Therefore, if the pit signal Sp by the inner rim side pit is positionedat a position corresponding to the constant value of the wobbled signal,the pit signal Sp by the outer rim side pit, recorded in associationwith another turn of the groove, is positioned in a manner irrelevant ofthe wobbled signal.

Referring to FIG. 9, the peak values of the pit signals Sp by the outerrim side pit, formed at the positions irrelevant to the wobbled signal,are varied from pit to pit, while the peak values of the pit signals Spby the inner rim side pits recorded at the constant wobbling positions,are constant.

If the peak values are constant, the peak values can be detected easilyby a simple peak-hold circuit, despite variations in the pit signalamplitudes, such that, by exploiting the detected peak values, the pitdetection level can be kept at an optimum level to enable stable pitdetection. This is a merit proper to the case in which pits are formedat substantially the constant wobbling amount.

Moreover, since the pit signals Sp are positioned at apices of thewobbled signal Sw, the tolerable variation width of the detection levelbecomes maximum. This is a merit proper to the case in which pitpositions correspond to the maximum wobbling and are proximate to theneighboring groove.

FIG. 10 shows an example in which synchronization signals Sws arerecorded in the wobbled signal and combined with the sync pits Ssp.

In this case, the positions of the sync pits Ssp can be previously knownfrom the synchronization signals Sws of the wobbled signal for assuringmore reliable detection of the sync pits Ssp. The following merits arederived from the above-described various combinations of the wobblingand the pits.

First, the case in which wobbling is in phase with the pits isexplained.

FIG. 11 shows a playback signal obtained from such optical disc. Theplayback signal is made up of the wobbled signal Sw and the pit signalsSp corrupted by noise components Sn.

FIG. 12 shows, in a block diagram, a reproducing apparatus forreproducing the wobbled signal and the pit signals.

In the present reproducing apparatus, the wobbled signal Sw is fed via aband-pass filter 31 to a convert-to-binary circuit 32, while the pitsignals Sp are fed via a by-pass filter 33 to a convert-to-binarycircuit 34, for conversion to respective binary signals.

The convert-to-binary circuit 34 outputs the pit signals Sp and thenoise components Sn, as shown in FIG. 11B.

The wobbled signal Sw is further sent to a phase comparator 35 for phasecomparison to a signal obtained on 1/M*100 frequency division by a 1/100frequency divider 37 and a 1/M frequency divider 38 of the oscillationfrequency of the voltage controlled oscillator 36. By controlling thevoltage controlled oscillator 36 by the phase information detected bythe phase comparator 35, a phase-locked loop is formed, asa result ofwhich a frequency Fo equal to (M*100) times the wobbled signal frequencyFw is outputted by the voltage controlled oscillator 36.

If the relation between the wobbling frequency Fw and the pit frequencyFp is given by Fw*M=Fp*N, the oscillation frequency Fo of the voltagecontrolled oscillator 36, given by Fo=Fw*(M*100)=Fp*(N*100), is equal to(N*100) times the pit frequency Fp.

Therefore, by frequency division of the output of the voltage controlledoscillator 36 by a 1/(N*100) counter 39, the phase information shown inFIG. 11C is obtained, and outputted to a pit pulse detectioninterpolation circuit 40.

By taking the AND of the phase information shown in FIG. 11C and theoutput of the convert-to-binary circuit 34, the noise components Sn arecanceled, as shown in FIG. 11D, so that bit data clocks shown in FIG.11E and the bit data as shown in FIG. 11F are outputted.

An example in which the synchronization (sync) signals are recorded inthe wobbled signal and combined with the sync pits is now explained.

Referring to FIG. 13, a wobbled signal shown at (a) isfrequency-modulated, and is demodulated to give a signal shown at (b).On the other hand, by arraying the sync of the pre-bit directly at backof the wobble sync, as shown at (c), the pre-bit sync can be detectedafter wobble sync detection.

The wobbling itself is not so accurate as the pre-pits. However, byproviding an arrangement of pre-pit protection by a system differentfrom one by the pre-pits, it becomes possible to improve safety of thepre-pit signal itself.

As a method of use other than gating, a leading end discriminationsignal of a pre-pit string can be inserted by wobbling, as shown in FIG.14.

The result is that there is no necessity of forming the sync pattern bypre-pits thus raising the pre-pit accuracy. Since there is no necessityof detecting the pre-pt sync pattern, circuit saving may be realized. Inaddition, the control circuit is duplicated, thus raising thereliability.

Although the foregoing description has been made of preferredembodiments of the present invention, it is to be noted that the presentinvention is not limited to these merely illustrative embodiments, butmay comprise various modifications or combinations.

For example, address pits 2 may be designed as ordinary pits.

If the sector information is recorded on both the wobbled signal and thepits, these may be used independently of each other. For example, it ispossible to exploit the address information by the pits before recordingthe signal and to exploit the address information recorded in themodulated state in the wobbled signal after recording the signal.

What is claimed is:
 1. An optical recording medium having: a wobbledgroove formed in the optical recording medium, the wobbled groove havinga sinusoidal shape, the sinusoidal shape defining a plurality ofwobbling periods; a land region of the recording medium betweenneighboring turns of the wobbled groove; and a plurality of pits formedcontinuously between neighboring grooves, wherein each pit interconnectsthe neighboring grooves.
 2. An optical recording medium as claimed inclaim 1 wherein a pit width in a rotational direction of the pits isformed smaller than the wobbling periods.
 3. An optical recording mediumas claimed in claim 2 wherein the pit is modulated by an on-off mode torecord address information.
 4. An optical recording medium having: awobbled grooved formed in the optical recording medium, the wobbledgroove having a sinusoidal shape, the sinusoidal shape defining aplurality of wobbling periods; a land region of the recording mediumbeing formed between neighboring turns of the wobbled groove; and aplurality of pits formed continuously on the land region so as to extendbetween and interconnect neighboring grooves together.